Influence of resin dies and resin auxiliary sheets on deep drawability of metal foil

The loading paths of blankholding pressure strongly influenced the limiting drawing ratio in deep drawing of metal foils. The limiting drawing ratio decreased as blank thickness decreased and it decreased rapidly below a certain value of blank thickness. The blankholding pressure required for the elimination of wrinkling increased rapidly as the sheet thickness decreased. As the blank thickness decreased, the area of the permissible loading zone of blankholding pressure decreased considerably. In the deep drawing of pure copper foils, the use of a PTFE die and a Nylon 66 auxiliary sheet was effective in the prevention of wrinkling. In this case, the clearance between the punch and die was set to be approximately 84.4% of the total thickness of the auxiliary sheet and foil blank. The Nylon 66 auxiliary sheet was subjected to ironing during deep drawing and the foil blank was subjected to strong compression in the thickness direction in the wall of the foil cup as well as at the flanges of the die shoulder, due to the action of the punch, Nylon 66 auxiliary sheet and PTFE die. Thus, the wrinkling could be prevented effectively. Meanwhile, in spite of this strong compression in the thickness direction, the significant decrease in the limiting drawing ratio was avoided due to the good lubrication that the PTFE die possesses in itself.